Mechanism for delaying release of bolt after firing a firearm



C. P. BERETTA Jan. 7, 1969 MECHANISM FOR DELAYING RELEASE OF BOLT AFTER FIRING A FIREARM l Filed March 17, 1967 INVENTQR. dnl.. Rum @man Amr,

United States Patent O 16,018/ 66 U.S. Cl. 89--193 4 Claims Int. Cl. F41d 5 08 ABSTRACT F THE DISCLOSURE A device, applicable to automatic and semi-automatic firearms is disclosed, for delaying the release of the breech bolt so as to adapt the operation of the bolt mechanism to different explosive powers of different cartridges, said device Ihaving the advantage of facilitating and rendering harmless the extraction of the spent shells.

This invention relates to a device for the delayed control of the bolt release in an automatic or semi-automatic firearm having a gas-intake port mechanism.

It is known, in automatic and semi-automatic firearms, to employ a fraction of the compressed gases evolved when firing a shell, in order to effect the operations of spent shell expulsion, 'cocking the firing pin mechanism and possibly also for feeding in a fresh cartridge.

The compressed gases, as evolved when tiring a cartridge are withdrawn, according to the conventional art, from the barrel through one or more ports and conveyed into a cylindrical chamber wherein they are allowed to expand thus causing a movable piston, housed within said chamber, to'be shifted, said piston being connected by a linkage to the mechanisms of the firearm intended to carry out the several operations enumerated above.

Under these conditions, the gases generated by the explosion and acting upon said piston, transfer thereto a drive which is a function of the pressure magnitude within the barrel, and also of the trend with which said pressure is varied in the course of time, said parameters being widely variable for each kind of cartridge usable in a single firearm.

Therefore, if rthe port through which the explosion gases are withdrawn and the linkage actuated by the expansion of the explosion gases has been calibrated soias to actuate said linkages when the firearm lires a weakly charged cartridge which is incapable of inducing high pressure within the barrel, then, as a more strongly charged cartridge is fired, the movable piston receives an exceedingly high thrust. If so, the controlled linkages of the firearm may be exceedingly stressed or too rapidly actuated. For example, the shell extractor can act upon the spent shell when a considerable residual pressure still obtains within the barrel, the result being a deformation or tearing of the shell casing base portion and thus the jamming of the weapon.

The object of the present invention is thus to provide a device for controlling the release of the bolt in a firearm, said device being actuated by the explosion gases and in which the release of the bolt is considerably delayed after firing the cartridge and so that a uniform operability is obtained in the care of cartridges having different explosive powers or different characteristics of the pressure trend of the explosion gases within the rearms barrel.

The inventive device comprises a cylinder communicating, through at least one duct, with the barrel of a firearm, a piston movable within said cylinder, an abutment member for stopping the movement of said piston away ice of said one duct, a body connected to the bolt of the firearm and capable of being shifted along a direction substantially parallel to the axial direction of said cylinder, means for guiding said body, and a spring urging said body towards said piston to abut with one end of said piston in the inoperative position.

Objects and features of the inventive device will become more clearly apparent in the ensuing exemplary disclosure of an embodiment thereof, as illustrated, without any implied limitation, in the accompanying drawings, wherein:

FIG. l is a diagrammatical partial longitudinal sectional view of a rifle to which the device is applied, in the inoperative position.

FIG. 2 shows a view in section similar to tha-t of FIG. 1 but with the device as actuated by the explosion gases.

FIG. 3 shows a cross-sectional view of the rie, taken along the line III-III of FIG. 2, and

FIG. 4 shows an axial sectional view of the detail of a piston actuable by the explosion gas and which is an integral part of the device.

FIGURES 1 and 2 show a barrel 1 of a rilie, aflixed, in any manner taught by the conventional art and not shown in detail herein to the breech or receiver 2 of the rifle, the drawings. In the receiver 2 is housed, in a freely slidable way, a bolt 3l carrying the usual tiring, extraction and feeding mechanisms as used in the automatic and semiautomatic firearms, these mechanisms being not shown in detail in the drawings in order to avoid overcrowding.

On the bolt 3 is active a spring 4 housed in a hole formed in the receiver adjacent the butt of the rifle.

To the barrel 1 is affixed, in an axially parallel position, a small cylinder 5 which can communicate with the barrel via the duct 6. Within the cylinder 5 is slidable a piston 7 whose stroke end positions are those shown in FIGS. 1 and 2.

As shown in FIG. 2, a stem 8 affords a further guidance to the piston and has, at one end, stop disc 9. The stem 8 is solidly aiiixed to the cylinder 5 by a nut 10. The piston 7 is shown in greater detail in FIG. 4. On examining FIG. 4 and FIGS. l and 2 conjointly, it can be seen that, between the piston 7 and the stem 8 a sealtight bushing 11 is inserted, which is held by a ring 12 on the piston 7. The piston 7 has, moreover, on its external surface labyrinth grooves 13 and has also slots 14 formed on the piston walls along the generating lines thereof.

In the neighborhood of the disc 9 is aixed a tube 1S which acts as a guiding member for a slidable sleeve 16 to which an arm 17 is solidly atiixed. The end 18 of the arm 17 is connected to the breech bolt 3.

The bushing 11 inserted between the stem 8 and the piston 7 is such as to permit that an imperfect coaxial relationship may exist between said stem and the cylinder 5, so as to render less stringent the necessity of a very accurate adaption of the component parts of the device during assembly and also to reduce the short-comings which might arise from slight defects of coaxial relationship between the stem 8 and the piston 7 due to Wear. The bushing 11 has, moreover, a somewhat wide flange so that the gas pressure acting thereupon may exert a compressive action by said anges on the piston surfaces adjacent thereto, the seeping of gases between the bushing and the piston being thus strongly reduced.

The operation of the subject device is thus as follows:

As shown in FIG. l when the device is in thev at rest position, the sleeve 16, due to the bias of the spring 4, `rests upon the piston 7 and shoves it towards the left, as viewed in the drawing. In this position the bolt 3 is closed and locked and the firearm is in readiness to fire.

As gas pressure develops in the barrel due to the firing of a cartridge, the gas passes through a duct 6 and urges the piston 7 towards the right until stop abutment 9 is reached, as shown in FIG. 2. During the movement from the left to the right of the piston 7, the sleeve 16 is thrust by said piston and, as the latter is stopped, it continues by inertia towards the right, first releasing the breech bolt locking mechanism and then thrusting the bolt backwards for a path length which is sucient (FiG. 2) to complete all the operations of expulsion of the spent shell and cocking of the firearm. These operations take place during the bolt recoil in a manner which is quite conventional and thus is not illustrated for the sake of simplicity.

On completion of these steps, the spring 4 restores the device from the position of FIG. 2 to that shown in FIG. 1.

The hollow configuration of the piston 7 serves the function of dampening the shock wave of the gases reaching the cylinder 5 and acts very much like an expansion chamber. This conformation of the piston 7 thus causes a delay in the movement of the piston with respect to the beginning of the gas into the cylinder 5.

Also the sleeve 16, initially upon being urged by the piston 7 towards the right as viewed in the drawings, disengages the locking mechanism of the bolt 3 and thus effects its displacement with a certain delay. A delaying influence in this particular direction is also experienced inasmuch as the speed of the displacement of the sleeve towards the right is decreased as soon as the urge transferred thereto by the piston 7 is discontainued. There is the additional advantage that the control of the bolt 3 and its attendant mechanisms is less abrupt than that of the prior art mechanisms, even if the piston 7 receives very energetic initial thrusts as a consequence of firing very powerful cartridges.

The slots 14 of the piston 7 have proven to be particularly useful to maintain the inner surface of the cylinder 5 free from incrustations even after firing a great number of shots. The left end portion (as viewed in the drawings) of the piston, made resilient by said slots, acts as a brake on the cylinder walls. the braking efficiency being the higher, the higher is the gas pressure acting upon the piston. This braking action unfolds a further smoothing effect when cartridges of different explosive power are used.

It is thus apparent that, by adopting the inventive device, even when using very powerful cartridges susceptible of inducing within the barrel very high instantaneous pressures, the bolt is always unlocked and displaced with a delay with respect to the entry of the explosion gases into the cylinder 5, so that the extraction of the spent shell from the barrel is not initiated before the elapse of a period of time sufficient to permit the gas pressure within the barrel to decrease to such an extent as to render the extraction of the shell easy and harmless. This situation is experienced also if the device is calibrated in such a way as to be capable of displacing the breech bolt even with comparatively weak cartridges.

The tube 15 on which the sleeve 16 is displaced can be used with advantage as a magazine for the cartridges which are introduced into the barrel in quite conventional a manner.

What is claimed is:

1. A device for the delayed control of the bolt release in a firearm, comprising a barrel and a bolt mechanism, wherein the device comprises a cylinder communicating through at least one duct with said barrel,

a piston movable within said cylinder,

a member for stopping the movement of said piston away from said duct,

a body connected to said body and displaceable in a direction substantially parallel to the axis of said cylinder,

means for guiding said body, and

a spring for urging said body against said piston to abut the latter with one of its ends to urge said piston to its inoperative position adjacent said duct,

said piston comprising a tubular wall closed at one end by a bottom wall,

said tubular wall having annular grooves formed on its outer peripheral surface, and

said tubular wall having slits formed along the generating lines and starting from the end of said piston wall.

2. A device for the delayed control of the bolt release in a firearm, comprising a barrel and a bolt mechanism, wherein the device comprises a cylinder communicating through at least one duct with said barrel,

a piston movable within said cylinder,

a member for stopping the movement of said piston away from said duct,

a body connected to said bolt and displaceable in a direction substantially parallel to the axis of said cylinder,

means for guiding said body, and Y a spring for urging said body against said piston to abut the latter with one of its ends to urge said piston to its inoperative position adjacent said duct,

said piston comprising a tubular wall closed at one end by a bottom wall,

said bottom wall having a hole formed therethrough and a sealtight bushing secured in said hole,

said cylinder having a stem extending longitudinally with respect to said cylinder, and

said stem being inserted through said bushing and the hole of said bottom wall in which said sealtight bushing is mounted.

3. A device according to claim 2, wherein said sealtight bushing has at its end which is directed towards the interior of said cylinder, a widened ange resting on the adjacent surface of said bottom wall.

4. A device as defined in claim 2, wherein said body comprises a sleeve,

said guiding means comprises a second sleeve mounted coaxially of said cylinder and slidably connected to the first-named sleeve to guide the latter for sliding movement coaxially of said cylinder, and

said member for stopping the movement of said piston comprises a stationary disc secured to said second sleeve to confront said cylinder, and to be engaged by said piston upon the movement thereof to its operative position.

References Cited UNITED STATES PATENTS 1,025,132 5/1912 Douglas 89-191 X 2,554,618 5/1951 Dixon 89-193 2,902,903 9/1959 Browning 89-191 3,058,399 10/1962 Allyn 89-191 3,200,710 8/1965 Kelley et al 89--191 BENJAMIN A. BORCHELT, Primary Examiner.

S. C. BENTLEY, Assistant Examiner. 

